In situ characterization of metals at extremes

The fundamental processes taking place in metals under extreme conditions can occur on ultrafast timescales (i.e., nanoseconds to picoseconds), and yet their result can continue to have a significant impact on the structural properties for many years to follow. The challenge in developing in situ methods for characterization under extreme conditions therefore involves both the modification of the instrumentation to implement the high-temperature, strain, and radiation conditions and the definition of the timescale over which the measurement must be made. While techniques are well established for characterization of the long-term effects of extreme conditions, experiments are only just beginning to probe the initial stages of structural evolution. This article reviews recent developments in optical, x-ray, and electron probes of metals under extreme conditions and also discusses the needs for future experiments and potential pathways to achieving these goals.